WHM load shows 62.25.43.22.46

My site normally will be down a couple of times a day, including WHM. During the down time of WHM, I can see that the load on WHM was showing as high as 66/43/22. Although the physical server was not down, but the websites are not accessible.

I wonder what causes the overload. I am pretty sure that there are only few people accessing the site during the down time. It normally takes about 3~5 minutes and then back to normal - down to 1.25/1.1/0.89.

I use CloudLinux to setup the CPU of 25% and 30 of concurrent connections. I also use CSF to enable syncflood_rate=20/s, syncflood_burst=10, portflood=22;tcp;5;300,80;tcp;20;3. However, it is still happening everyday.

I have a 4 cpu Q9550 2.83GHz and 6GM memory server. So, it should be enough.

Does any one know what might cause this issue and how do I track what's the process causing the overload? Thank you very much for your help.